Method and apparatus for seismic signal pattern discrimination

ABSTRACT

A method for extracting predetermined types of seismic data from an overall composite of seismic information, the method consisting of constructing an ideal filter for each of selected primary, multiple and/or interference components of a seismic tract group, such filter construction being carried out by determining the pseudoinverse or generalized inverse of a polynomial matrix as determined for the particular seismic traces to be examined, with application of the polynomial matrix for preadjustment of a multichannel pattern discriminating filter which, when energized by the input seismic traces under examination, will produce separately the requisite primary, multiple and interference outputs which represent the respective components present. Apparatus for carrying out the method may consist of plural channels of time domain filters connected in series with a weighting device for convolving respective plural seismic traces; each of the convolution filters is adjusted to function at predetermined times and amplitudes in accordance with the matrix function or operator determined for primary, multiple and interference trace functions of a particular group of seismic traces.

Il'nited Mates Patent Goupiillllaud [451 Mar. 28, 11972 [54] MIE'I'I-IDDAND APPARATUS FUR SEISMIC SIGNAL PATTERN DICRIMINATIUN [72] Inventor:Pierre L. Goupillaud, Ponca City, Okla.

[73] Assignee: Continental Oil Company, Ponca City,

Okla.

[22] Filed: Aug. 111, 11969 [21] Appl. No.: 848,777

[51] 111112.021. ..G0l1v 1/116,G01v 1/28 [58] Field of Search..340/15.5,15.5 F, 15.5 AF,

340/155 GC,15.5 CC, 15.5 SC

[56] References Cited UNITED STATES PATENTS 3,311,874 3/1967 Sheffield..340/15.5 FC

2,979,692 4/1961 Grannemann et a1. ..340/15 5 3,344,396 9/1967 Bennett340/15 5 3,396,365 8/1968 lierns ..340/15.5

3,430,193 2/1969 Lindsey et a1 ..340/15.5

3,437,999 4/1969 Landrum, Jr. ..340/15.5

FORElGN PATENTS OR APPLICATIONS 162,327 3/1963 U.S.S.R. ..340/15.5

Primary Examiner-Rodney D. Bennett, Jr.

Assistant Examiner-N. Moskowitz Attorney-Joseph C. Kotarski, Henry H.Huth, Jerry B. Peterson, William J. Miller and David H. Hill A methodfor extracting predetermined types of seismic data from an overallcomposite of seismic information, the method consisting of constructingan ideal filter for each of selected primary, multiple and/orinterference components of a seismic tract group, such filterconstruction being carried out by determining the pseudoinverse orgeneralized inverse of a polynomial matrix as determined for theparticular seismic traces to be examined, with application of thepolynomial matrix for preadjustment of a multichannel patterndiscriminating filter which, when energized by the input seismic tracesunder examination, will produce separately the requisite primary,multiple and interference outputs which represent the respectivecomponents present. Apparatus for carrying out the method may consist ofplural channels of time domain filters connected in series with aweighting device for convolving respective plural seismic traces; eachof the convolution filters is adjusted to function at predeterminedtimes and amplitudes in accordance with the matrix function or operatordetermined for primary, multiple and interference trace functions of aparticular group of seismic traces.

ABSTRACT 10 Claims, 9 Drawing Figures METHOD AND APPARATUS FOR SEISMIESIGNAL PATTERN DISCRIMINATION BACKGROUND OF THE INVENTION 1. Field ofthe Invention The invention relates generally to seismic signalprocessing systems and, more particularly, but not by way of limitation,it relates to improved seismic signal processing apparatus which iscapable of extracting predetermined forms of signal information from anoverall seismic trace group.

2. Description of the Prior Art The prior art includes various types ofseismic trace processing systems which perform various modes andcombinations of filtration procedure such as frequency responsivefiltering, correlation filtering, velocity filtering, etc. Many attemptshave been made at construction of an ideal filter for receiving a givenset of seismic trace values therethrough in the expectation that theideally filtered trace signal might possibly be existent at the output.However, the prior filtration teachings, as well as the practicalapplications, have depended upon various methods of attenuating unwantedsignals through one or more limiting operations, this also resulting indegradation and loss of valuable seismic information at the same time. Asuccessful approach at actual extraction of desired seismic informationfrom a series or train of seismic signals has been elusive but thepresent invention sets forth a method for efiectively separating outdesired information and completely eliminating unwanted seismic signalreturns.

SUMMARY OF THE INVENTION The present invention contemplates method andapparatus for processing of seismic signals wherein sample field data isemployed to construct a multi-channel pattern discriminating filterwhich reduces seismic trace input data to the respective contributingfactors of primary, multiple and interference data components. In a morelimited aspect, the invention consists of applying each of a pluralityof input seismic traces to a respective time domain filter having itsweights adjusted in accordance with an operator determined by apseudoinverse matrix function. The outputs of respective time domainfilters are then summed to form a distorted representation of respectiveprimary, multiple and interference components of the input seismictraces, whereupon further recursive filtering in accordance with aspiking operator provides desired output information.

Therefore, it is an object of the present invention to provide a signalprocessing system which approaches ideal signal filtration throughextraction of desired signal information.

It is also an object of the invention to provide an apparatus forextraction of a specific type of seismic signal return from extremelyscrambled and masked over signals.

It is a further object of the invention to provide a method andapparatus capable of extracting and separating primary, multiple and/orinterference signal components from a seismic trace group.

Finally, it is an object of the present invention to provide method andapparatus for extracting predetermined signal information from a seismictrace group with no degradation or loss of the specific traceinformation sought.

Other objects and advantages of the invention will be evident from thefollowing detailed description when read in conjunction with theaccompanying drawings which illustrate the invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. IA is an algebraic matrixconstructed in accordance with the invention;

FIG. IB is an algebraic matrix representing a pseudo-inverse entity asconstructed for operation in the invention;

FIG. 2 is a block diagram of a multi-trace signal processing systemconstructed in accordance with the invention;

FIG. 3A is a derivation of signal trace values to be used in accordancewith the present invention;

FIG. 3B is a functional diagram illustrating the operations performedupon the trace input values of FIG. 3A, in accordance with the matrix ofFIG. 1B.

FIG. t is a block diagram of analog apparatus for carrying out seismictrace processing in accordance with the invention;

FIG. 5 is a block diagram of one form of a time domain filter which maybe employed in the system of FIG. 4;

FIG. 6 is a block diagram of additional signal processing circuitryconstructed in accordance with the invention; and

FIG. 7 is a block diagram of alternative seismic signal processingcircuitry which may be employed in place of the processing circuitry ofFIG. 6.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The present system isdirected to a method and apparatus which is capable of unscramblingreceived information in order that a more meaningful interpretation canbe isolated or indicated. Such procedure may be likened to unscramblingtechniques as employed in other technologies wherein electrical signalscrambling may be the result of predetermined coding schemes, suchintentional scrambling being capable of reversal with designatedunscrambling equipment for reconstitution to its original form. However,in the case of seismic information, the scrambling is due to naturalcauses which tend to defy analysis into the various sub-components ofthe overall signal indications. In such case, a discrimination of thesub-components of returned seismic signal energy must rely upon analysisin terms of probability of occurrence of the particular components for aselected terrain.

The present invention contemplates a solution to the problem by means ofa scheme which is best defined in mathematical terms. Thus, a pluralityof seismic traces, i.e. such as recorded at various detector locations,will comprise common components which are shifted by varying amountsfrom trace to trace. For example, a first trace may comprise threecomponents as S,(t)=p(r)+m(r)+i(r) (I) where 1(1) represents the primaryreflection component, m(t) is the multiple reflection component, andi(t) is the surface wave or interference component. Remaining ones of atrace group, e.g. a four trace seismic data group, might be representedas where, as may be seen, various components are shifted in time byknown amounts 2 where i is an index for the trace and j an index for thecomponent.

As is well known in the art of sampled data analysis, by means of thez-transformation, equation (1) may be represented as the series S(z)=S,(O)+S (lAr)z-l-S,(2At)z (3) whereupon the polynomialrepresentation for the entire four trace group becomes a row vector ofpolynomials S1 4 1( 2( 11(2) 4(2)] and equation (4) may be furtherdesignated or rewritten as l 1 l 1 S X =[p(z), 111(2), i(z)] |:1 2 2 2 1=C X Z X4 1 :32 raa t34 x4 wherein C is a row vector comprising thethree polynomials representing the three components. The purpose of theideal filter is to retrieve C x 3 from S The matrix 2 is called thepattern matrix and it is represented in expanded form in FIG. 1A. Thus,given that 1x4 CIXB 3x4 then it may be postulated that there exists amatrix Z" 3 such that SD44 4x3 ixs 3 4 4x3 CIXS axa l 3 This is true ifBut, clearly, if 2 Z' (ZZU' then,

3x4 axs 3x4 4xs) sxa 3x3 22+ where 2'', represents 2 transpose, awell-known matrix operation.

It will then follow that we must define Z AZUZZ 10 and this is alwaystrue because of the existence of the regular inverse of a symmetricmatrix. The resulting polynomial representation, as shown in equation(10), is what may be referred to as a generalized inverse orpseudoinverse of a rectangular matrix. The matrix or the pseudoinverserepresentation of Z is represented in its fully expanded form in FIG.18.

Since the elements of the matrix are polynomials, the elements of thepseudoinverse will be ratios of polynomials as shown in FIG. 1B. Thepolynomial denominator 11B of all the pseudoinverse elements will be thesame, the determinant of the matrix (22'). The value Z is indicative ofthe operation which must be performed on selected seismic trace inputsS,(t S.,(t). Each column 12, 14 and 16 of the pseudoinverse matrix Zcharacterizes a series of operators, one operator for each of the inputseismic traces.

Aa is well known in sampled data systems, the Z transform of an inputseismic trace S,(t) has been defined above by equating it to the seriesS,(z)=S,+S, (At)Z+S, (2At)Z ..etc. 11 This transformation indicates thatthe Z variable is a shifting operator; that is, multiplying a polynomialcorresponding to a signal by 2 corresponds to shifting the signal by ntimes the sampling interval. Thus, the individual rows of respectivecolumns 12, 14 and 16 of the matrix Z each represent a time domainoperator within the filtering scheme which will be peculiar to aselected set of input seismic trace values.

The block diagram of FIG. 2 illustrates the various sub-components ofone form of system for processing multiple trace inputs to derivespecific information as to primaries, multiples, and interference signalindication. Thus, the signal processing system 31 receives input seismicsignal at input leads 32, 34, 36 and 38. Input leads 32-38 receiverespective ones of a multiple of seismic traces, in this case fourtraces, but the number of inputs will vary with exigencies, which arethen applied in parallel to each of respective primary processingchannel 40, multiple processing channel 42 and interference processingchannel 414. Primary processing channel 40 includes a pattern filter 46which provides a summed output to a spiking or recursive filter 48 withoutput of primary seismic signal indications at output 511. Similarly,the multiple processing channel 42 receives plural trace inputs at apattern filter 52 which provides a summed output to a spiking filter 54with resulting multiple indications at output 56, while interferenceconvolution takes place in a pattern filter 58 with output throughspiking filter 611 to an interference indications output 62. Actualdisposition of related operation functions is illustrated in FIGS. 3Aand 38 as will be further described below.

The pattern filters 46, 52 and 58 may be any of various wellknown timedomain filtering equipments and the spiking filters 4%, 54 and 611 mayalso be conventiona. hardware finding general availability in therelated art. The pattern filters 36, 52 and 53 for a four trace inputare shown with greater particularity in FIG. 4. Each of the patternfilters 4-6, S2 and 58 consists of a plurality of individual time delayswhich provide plural outputs to a respective weighting network.

Thus, pattern filter 46 is comprised of plural time delay units, in thiscase four such time delays 64, 66, 68 and 70 connected in parallelrelationship, and each providing plural channel outputs 72, 74, 76 and78 to the respective weighting networks 81), 82, 8 1, and S6. The outputfrom weighting networks 311', 82, 84 and as are individually summed foroutput via leads 88, 911, 92 and 94 for further summation in a summationnetwork 96 for output on a line 923 as the C, data value. The C valueexists in convolution with an operator value representative of a timeanalog function indicative of primary reflection seismic signals withinthe S,(t) S.,(t) trace information.

One form of time delay unit and associated weighting network which maybe employed in the pattern filters is a conventional type as shown inFIG. 5 Thus, a suitable recording drum receives trace input via lead1112 and a recording head 104 while successively delayed outputs areremoved at later times by time-displaced reproducing heads 1106, 11%,111), 112 and 114. Respective ones of the differently delayed traceoutputs from reproducing heads 1116-1141 are then present on leads 116,118, 1211, 122 and 12 3 for input to respective weighting networks 126,128, 131i, 132 and 136. The weighting networks 126-134 may beconventional circuitry designed for carrying out such attenuationfunction, and the outputs from the plurality of weighting networks126-134 is summed along a single output line 136 for application to thenext stage in the present case for application to the summation network96 of FIG. 4.

Referring again to FIG. 4, each of the multiple processing channel 52and the interference processing channel 5% may be constituted similar tothe primary processing channel 36, i.e. a time delay means and weightingnetworks similar to the structure of FIG. 5 may be employed. The weightsof each of the networks of each channel are given in the pseudoinversematrix 2*. Thus, each of the trace inputs 32, 34, 36 and 38 is appliedto the pattern filter 52 with input to respective time delay means 141,142, 144 and 1 56 which, in turn, provide respective pluralities ofoutputs 148, 151), 152 and 15 1 for input to respective ones ofweighting networks 156, 158, 1611, and 162. The outputs from weightingnetworks 156-162 are then summed on output leads 164 166, 168 and 1711for further summation in a summation network 172 to provide an output Con lead 174, output C constituting data convolved with the multipleoperator function, indicative only of multiple energy.

The pattern filter 58 is connected in the identical manner with traceinput leads 32-38 applied through respective time domain filters 1'76,1'78, and 182 to provide plural individual outputs on respective leadgroups 184, 186, 188 and 190 for input to weighting networks 192, 19 3,196 and 198. Outputs from weighting networks 192-198 are summed onindividual output lines 2611, 202, 204 and 2116 for further summation insummation network 2115; to provide a C output containing interferencedata on a lead 210.

It should be understood that while each of the lead groups 72-78,148-154 and 18 1-1911 are shown as including five individual andparallel leads, this is merely a generalization and this number can varywithin wide limits depending upon the operator function being utilized.The actual number of parallel leads and associated attenuator for eachtrace input of each of the pattern filters 46, 52 and 58 will dependupon the specific operator as derived from the operating matrix. Thus,the functional diagrams of FIGS. 3A and 3B show the time and amplitudecharacteristics of the trace inputs and operators as derived from thematrix of FIG. 1.

FIG. 3A illustrates the input trace functions for primary, multiple andinterference signal input in accordance with the matrix function of FIG.1A. Thus, S,(t) is derived in column 211 with each of primary, multipleand interference wavelets being represented with no time delay along therespective time z axes. The summation 211a, A,(t) p(t) +m(t) +i(l) maythen represent the trace input S,(t) for application through theoperator derivations of FIG. 3B.

Similarly, traces 5 (2), S -,(t) and S,,(t) are derived in like mannerby algebraic summation of the respective primary, multiple andinterference time analog values in each of columns 213, 215 and 217. Ineach case, the trace values 213a, 215a and 217a represent the respectiveS (t), 5 (1) and S (t values for operation application as shown in FIG.3B. Noting the time axes of the various traces, it can be seen that theZ matrix exponent values represent the time delay for each waveformmaking up the matrix representation, and each summation or trace inputA,(t) through A (t) embodies the respective delay characteristics.

The functional diagram of FIG. 38 illustrates the time versus amplituderelationship of the various input seismic traces, their respectiveprimary, multiple and interference operators in the 2'" matrix, and thefinally derived component operators (1,, C and C Each of the waveformsin FIG. 3B is represented as a time analog waveform of predeterminedsignal content, and such waveforms as the pattern operators withinpattern filter stages M2, 214, and 216 may be directly identified in the2* matrix of FIG. llB as described hereinafter.

Thus, the respective input traces or seismic signals 5 (1) through S 0),identified as input trace signals 2118, 226), 222 and 224, are indicatedas being of equal time length, i.e. from zero to 12 time intervals, suchintervals being indicated by the plurality of interval markers 226. Theexact length of the time intervals is immaterial as the resultingoperators will still be a relatively equatedfunction of the input tracesignal.

Pattern filter group 2ll2 illustrates, and again on similar time scale,the respective operators selective of primary reflection characteristicsare described by traces 229i, 231i 232, and 234; and it may be notedthat they are of quite different waveform. A comparison of therespective matrix quantities 118p, 20p, 22p and 241p of FIG. TB willindicate the transposition similarities. It may be noted that operatorwaveform 223 is merely a graphic representation of matrix quantity lifipwith consideration given to polarity, amplitude multiplier, and with theexponent being directly related to the time interval of the sample.Thus, there being no indications for exponents zero through four ofmatrix quantity mp, the first quantity is lZ which is shown at the fifthtime interval marker 236 (FIG. 3) by a unitary negative excursion. Thesimilar graphic representations are made for each of the remainingexponents or time interval values through Z at interval marker 238. Itshould be noted too that exponents omitted from matrix quantity 18p,e.g. Z and Z values, are merely zero indications and are noted as suchby the respective ninth and tenth time interval markers 240 and 242.Similarly, the respective operator waveforms 230, 232, and 234 aredirectly identifiable as matrix values 20p, 22p, and 24p.

In the same manner, operator waveforms selective of multiple reflectionenergy characteristics are described by the operator waveforms 2M, 2456,2th and 256 in the pattern operator group 2M. The operator waveforms 24.4 through 250 may be equated to the matrix values 18 2 h, 22, and 241 ofcolumn 14 in FIG. 1B. The multiple energy operators 2 2L250 extend overa shorter time span than do the primary operators in pattern group 212,and this is simply due to the nature of the pattern of particularmultiple reflections chosen in this example. As can be noted frompattern group 216, the operators selective of the interference allpersist for a relatively longer time duration. Each of interferenceenergy operators, waveforms 252, 254i, 256 and 253, are traceable andidentifiable as the matrix quantities T8,, 24),, 22, and 24, of columnto of the matrix of FIG. llB. The interference operator values areappreciably longer tending to extend upwards to the 2tlth exponent whileretaining meaningful signal identifying changes. This also is due to theparticular interference pattern characteristics selected in thisexample.

FIG. 38 illustrates the further summation of operators as derived fromthe summation networks 96, 172 and 208 (FIG. 4 to provide the respectivecomposite primary, multiples and interference operators C C and C Theseoperators 260, 262, and 264 may also vary in time duration; however,this will be a function of the individual contributors within therespective pattern filter groups 212, 214 and 2116 as derived from theoriginal signal inputs.

Trace representations having undergone operation in accordance with thefunctions as represented by waveforms 260, 262, and 26 1 then requirefurther processing. At this point, the input traces 3 (1) S (t) haveexperienced convolution with properly determined operators, and thesubsequent summation of the time domain filter outputs produces for eachchannel, a signal which contains no energy fitting the other wavepatterns. This waveform represents the primary component convolved withthe denominator of operator l0, and similarly for the other componentwaveforms. It is then necessary to recompress the trace information andthis can be done by determining a spiking operator with delaycorresponding to denominator if) of the matrix of FIG. 1B. This spikingoperator is then convolved with each of the summation trace operatorfunctions C,, Q and C to obtain the component of the input signals whichadheres to the particular pattern.

Such spiking operator convolution is carried out by means of the spikingfilters 48, 54 and 60 (FIG. 2), and as shown in greater detail in FIG.6. The three spiking filters 48, 54 and 60 are identical and consist ofa time domain filter operating through a suitable weighting network.Thus, spiking filter lfl receives the C operator input for applicationto a time domain filter 270 which output is weighted in a denominatorweighting network 272 to provide a signal output 274i representative ofprimary trace signal characteristics pH). The multiple information or Cinput is applied through a time domain filter 276 and then to adenominator weighting network 278 and multiples information output 280.Similarly, G input is applied through a time domain filter 282 andseriesconnected denominator weighting network 284 to provide aninterference information output 286. Each of the spiking filters 48, 54and 60, which comprise a time domain filter and denominator weightingnetwork, may be conventional equipment as illustrated in FIG. 5.

Similar operator values are adjusted into each of the weighting networks272, 278 and 28 3. Such operator may be termed the spiking operator Dwhich is an approximation of the reciprocal of the denominator of Z ordenominator ltl of the matrix of FIG. 1. Thus, if the denominator D isconsidered as a sequence as d d d d a rectangular matrix A (n m l, m)can be constructed from the operator D. That is, in accordance withconventional spiking filter design, and much in the same manner as wasfollowed in constructing the previous matrix 2", the matrix identity AA.can be used such that a spiking operator can be extracted from A. In thedetermination of A, loading of the diagonal of (ED) can be used toobtain more stable operators. Thus, the center row of the pseudoinverseA will give another sequence d,,, 41' d' d' representative of thespiking operator function which, upon filtering with one of the tracesresulting from the first convolutions, will produce proper energycomponents along each of the selected energy patterns. Referring to FIG.6, each of the time domain filters 270, 276 and 282 and respectivedenominator weighting networks 272, 278 and 284 are similarly adjustedin accordance with the recursive filtering characteristics as determinedfrom a selected center row of matrix A That is, the respective timedelay outputs from each oftime domain filters 270, 276 and 282 will beanalogous in number and delay and, subsequently, the delayed outputs areapplied to respective equally Weighted attenuation networks within eachof the denominator weighting networks 272, 278 and 2554 OPERATION Themethod and apparatus of the present invention may be employed to processmultiple trace seismic information to extract energy componentsrepresentative of specific forms of return signal, e.g. primaryreflective energy, multiples reflective energy, interference or groundwave energy, etc. Prior to setting up the equipment or apparatus of theinvention, some information of the terrain, i.e. relative to thatterrain from which the seismic information under examination wasderived, should be available to allow pre-seeting of the apparatus. Asample of the seismic information may be examined to isolate a selectedhyperbola of events which will enable determination of relative t (timeshift) values. Such r time shift values are the known quantities whichprovide a numerical base upon which the entire unscrambling process canfunction to isolate and extract the different forms of seismicinformation.

The apparatus of FIGS. 4 and 6, adjusted in accordance with operatorvalues such as shown in FIG. 3B, operate to extract specific forms ofseismic information. The graphic waveform representations of F 16. 3Bare merely a time analog representation of the operating matrices fromFIG. llB which may be applicable to a particular set of input seismictraces. Thus, for a given set of input traces as S (t) S (t) (FIG. 3A),and for known t or time shift values as derived from inspection ofpertinent seismic data, a matrix can be constructed such as that shownin FIG. 113. Having determined the set of delays t 10 (equation 2) themethod then proceeds with building the matrices related to the t valuessuch that each element of the matrix is a symbolic variable 2 elevatedto the power I in the present case selection of as determined fromconsideration of equations (1) and (2) resulted in the conclusion thatsuch that the pseudoinverse of Z is equation (10), such pseudoinversevalue Z being fully expanded in the matrix of FIG. ll.

The matrix values represented in FIG. ll can then be set into thevarious time domain filters within respective pattern filters 3O 46), 42and 44! of FIG. 4. The matrix of FIG. 11 can be broken down such thatcolumn 112 represents primary information, column 14 represents multipleinformation, and column 16 represents interference information, and thevarious matrix values can be adjusted into the respective time domainfilters of pattern filters 46, 52 and 5? The matrix values 18p, 20p, 22pand 24p provide time delay adjustment to respective time domain filters64, 66 and 68 and 70. That is, the 2 variable of the shifting operatorcorresponds to shifting the signal by n time sampling intervals suchthat the exponents of the Z value functions with final summation ofextracted primary, multiple 0 and interference information in therespective summation networks 96, 1172 and 208 to provide output signalson leads 9%, i174 and 210. The respective primary, multiples andinterference outputs C C and C processing.

Each of the seismic information signals (1,, C and (I contains thedesired extracted seismic information, but it is convolved with theoperator function corresponding to the denominator. instead of using thespiking filter described earlier, it is also possible to further subjectthe signals to recursive filtering to isolate the desired information;this can be brought about by subjecting each of the C, C output signalsto a recursive filter operation which adheres to the tirne-amare thenready for further 2743, 284]) and 286 and they represent the extractedprimary, multiple and interference information traces, respectively.

lit should be understood that while an analog apparatus in fullydescribed and set forth herein, the performance of the method may alsobe carried out by digital computer apparatus which is specificallyprogrammed for the seismic information extraction operation. Suchdigital computation can be generally relied upon to require input of twodistinctly different program outlines. Thus, a first program operates tocon struct the desirable filters, i.e. the various time domain filterswhich adhere to the requirements as determined by the optimumcontrolling matrix, and a second program is employed in coordinating theconstructed filter in its operation on the input seismic data.

While the method and apparatus has been more particularly describedrelative to input of four seismic traces, it should be understood thatany number of seismic traces may be employed, various peripheralconsiderations dictating the number and application of traceinformation. The selection of processing methods may vary within a widerange of limits depending upon the exigencies of each particularapplication, not only the logistics of the terrain and requiredinformation, but also the secondary considerations of requisite time, intended employ of the information, etc.

An alternative procedure consists of utilizing the apparatus of H6. 7 inseries with that of FlG. to substitute a different recursive filteringof the C C and C outputs on leads 93, 1'74 and 210. Thus, the respectiveoutput leads $8, 1174 and 2M) (FIG. 4) are applied to an input selector2% which selects one of the C C and Q inputs for application to anoperational amplifier 292 which receives controlling feedback input viaa lead 294. The output of operational amplifier 292 is applied to adelay line 296 which provides a plurality of outputs 293, each delayedby successively greater amounts with input to a selected one of theadjustable, phase-sensitive attenuators ass. Output from each of theadjustable attenuators 300 is applied via lead 294 for feedback throughthe operational amplifier 292 while final output from delay line 296 isapplied via lead CW2 to a suitable output device 3% e.g. recorder,camera, oscillograph, etc.

The delay line 296 and the plurality of attenuators 300 combine toproduce reverse recursive filtering such that an output at 3M2 willcontain the component of the original input ((3,, C or C which fit theapplicable operator pattern. It may be noted, in this case, that thedelay line 2% and attenuators 3600 are set in accordance with thedenominator of Z or the matrix denominator llil (FIG. ll) withoutrequiring any further determinations. Thus, proceeding left-to-rightacross the successive delay outputs 298 of delay line 296, each of theattenuators 300 can be likened to the proper amplitude ratio of the Zdenominator, polarities being reversed due to the reciprocal nature ofthe quantity.

There are various other analog devices which may be employed in carryingout the method of the invention. Thus, while specific reference is madeto the time domain filtering concept and well-known forms of tape delaymeans and associated weighting networks, there are any number of various0 record delay units, acoustic delays, cathode ray filters, and

plitude qualities of the denominator M) of the matrix of FIG. 1.

This will be shown later in conjunction with FIG. 7.

When using the spiking filter, the denominator pseudo-inverse A' isdetermined in well-known manner for employ in adjusting the variousconsecutive time delays and series-connected weighting networks ascontained filters 48, 54 and 60 ofFiG. 6. Each ofthe C C and C inputsreceives the similar operator convolution, and the desired extractedinformation is presented at the output of denominator weighting networks272, 278 and 284; that is, a summation of in each of the spikingweighted output signals are present on each of output leads such relateddevices which may be coupled with suitable forms of weighting amplifiersor attenuators to perform the requisite functions of convolving an inputsignal with a predetermined time-changing operator value. it should beunderstood too that the processing method of the present invention maybe combined with other known types of signal enhancement technique toperform additional functions upon extracted seismic information; suchadditional processing providing the possibility of extremely accurateand detailed analysis of seismic signal return energy.

The foregoing discloses a novel method and apparatus which may be usedfor treating seismic signal return energy in dication in a mannerwhereby specific information is extracted without loss or degradation ofthe product signal energy. The method can be performed in the laboratoryor more directly in the field, and analog, digital, or certaincombinations of analog-digital equipment may be employed in carrying outthe processing method. The present method has the advantage of providingan information extraction approach to seismic signal processing asfurther coupled with the capability of processing reasonably large timeincrements of seismic data.

Changes may be made in the combination and arrangement of steps asheretofore set forth in the specification and shown in the drawings; itbeing understood that changes may be made in the suggested structuredisclosed without departing from the spirit and scope of the invention.

What is claimed is:

i. A multi-trace pattern discriminating filter for processing pluraltraces of related seismic data, comprising:

input means receiving said plural traces of seismic data;

first second and third pattern filter means each receiving said pluraltraces of seismic data and each providing a time analog signal outputwhich is representative of respective components of primary, multipleand interference reflection energy, each pattern filter means includingplural time domain filter means each receiving a different one of saidplural traces as input and each providing a plurality of time delayedoutputs which are delayed by a different time, and each including pluralweighting networks each functioning in accordance with a characteristicoperator determined by the pseudoinverse matrix function for seismicenergy traveling a selected path and each receiving one of saidpluralities of time delayed outputs from a respective time domain filtermeans to provide a summed output, and each such filter also includingsummation means receiving the summed output from each of said pluralweighting networks to provide a further summed time analog signalindicative of reflected seismic energy representative ofa selectedcomponent; and

output means selectively providing a record and indication of each ofsaid first, second and third time analog signal outputs.

2. A multi-trace pattern discriminating filter as set forth in claim llwherein said output means comprises:

time domain filter means for selectively receiving summed output fromone of said summation means to generate a plurality of time displacedoutputs each delayed by a preselected different time; and

spiking weighting means receiving each of said time displaced outputs toefiect preselected polarization and attenuation in accordance with timedelay position, and to sum all displaced and attenuated outputs toprovide a time analog output signal indicative of a selected componentof reflection seismic energy.

3. A multi-trace pattern discriminating filter as set forth in claim lwhich is further characterized in that:

each time domain filter of said first pattern filter delays eachrespective one of the plurality of time delayed outputs by the sameincrement;

each time domain filter of said second pattern filter delays eachrespective one of the plurality of time delayed outputs by the sameincrement; and

each time domain filter of said third pattern filter delays eachrespective one of the plurality of time delayed outputs by the sameincrement.

4. A multi-trace pattern discriminating filter as set forth in claim llwherein each of said weighting networks comprises:

a plurality of attenuators each receiving a selected time delayed outputto generate an attenuated output, each attenuator adjusting a respectivetime delayed output to a selected magnitude which is said function of acharacteristic operator for a selected component of the particular oneof said plural traces which were applied to the respective time domainfilter providing said time delayed outputs; and

attenuator summing means receiving attenuated outputs from each of saidplurality of attenuators to provide said summed output.

llil

5. A multi-trace pattern descriminating filter as set forth in claim 4wherein said output means comprises:

claim ll wherein said output means comprises:

selective input means for receiving a selected one of said time analogsignal outputs;

operational amplifier means receiving said time analog signal output foramplification to provide an output voltage, said amplifier meansincluding a feedback input;

a delay line having plural, time displaced outputs and a signal outputand receiving said output voltage at an input;

variable attenuating means each connected between a different one ofsaid time displaced delay line outputs and said feedback input, saidattenuating means for each time displaced output being set in accordancewith a preset time analog operator;

an output device receiving said delay line signal output forrepresentation as a selected energy component within said multipletraces of seismic data.

7. Apparatus for processing multi-trace seismic information by effectingexclusive extraction of plural data indications each havingpredetermined energy characteristics, comprising:

means for dividing said multi-trace seismic information into plural,parallel groups of plural trace inputs;

first convolution means receiving a first group of said plural traceinputs for separately convolving each input with a trace operatorrepresentative of time and amplitude characteristics for energytraveling a first selected path to generate a respective convolutionoutput for each of said trace inputs;

second convolution means receiving a second parallel group of saidplural trace inputs for separately convolving each input with a secondpredetermined trace operator representative of time and amplitudecharacteristics for energy traveling at a second selected path which isdifferent from said first selected path to generate a respectiveconvolution output for each of said trace inputs;

third convolution means receiving a third parallel group of said pluraltrace inputs for separately convolving each input with a thirdpredetermined trace operator representative of time and amplitudecharacteristics for energy traveling a third selected path which isdifferent from said first and second selected paths to generate arespective convolution output for each of said trace inputs; and

a plurality of summation means for separately summing the pluralconvolution outputs from each of said first, second and thirdconvolution means to generate first and second generalized indicationsof trace energies along said first, second and third reflection paths.

8. A method for processing multi-trace seismic information by effectingexclusive extraction of plural data indications each havingpredetermined energy characteristics, comprising the steps of:

dividing said multi-trace seismic information into plural parallelgroups of multi-trace inputs;

convolving each trace of each group with a predetermined operator whichis representative of time and amplitude of energy traveling a selectedpath as determined by the pseudoinverse matrix function for the selectedpath, the respective operators of a first group representing primaryreflection for each trace, the respective operators for a second grouprepresenting multiple reflection for each trace;

separately summing convolved traces of each group to provide a groupconvolution trace representing reflection characteristics for selectedseismic energy forms traveling selected paths.

9. A method for processing multi-trace seismic information by effectingexclusive extraction of plural data indications each havingpredetermined energy characteristics, comprising the steps of:

dividing said multi-trace seismic information into plural,

parallel channels;

convolving each input of multi-trace information from first and secondchannels with respect to first and second predetermined time analogoperators representative of primary and multiple components ofreflection energy as determined by the pseudoinverse matrix function forthe respective energy components to produce first and second outputrepresentations neither of which contains any indication of energycommon to the other;

recompressing said first and second output representations to obtain anindication of the primary and multiple components of energy,respectively.

W. A method as set forth in claim 9 which is further characterized toinclude the steps of:

convolving each input of multi-trace information from a third channelwith a respective third predetermined time analog operatorrepresentative of an interference component of reflection energy toproduce a third output representation containing no indication of energycommon to that of said first and second output representations;

recompressing said third output representation to obtain an indicationof the interference component of energy within said multi-traceinformation.

t um-ma i g g r "with STATES PATENT oFflcE eETmcA 0F Patent No.3,652,980 D ted March 28, 1972 Invencor(s) Pierre L. Goupillaud.

It is certified that error appear in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

Column 9, line 68, should read:

--selected magnitude which is a function of said charac--- Signed andsealed this 29th day of August 1972.

(SEQAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT G-OTTSCHALK Commissioner of- PatentsAttesting Officer $2223? UNTfEb ISTATEQV PATENT .OFFIHCE CERTIFICATE OFCORRECTION Patent No- 5,652,980 D te March 28.. 1972 Inventor(s) PierreL. Goupillaud.

It is certified that error appeare in the ebove-identified patent andthat said' Letters Patent are hereby corrected as shown below:

Column 9, line 68, should read:

--selected magnitude which is a function of said charac- Signed andsealed this 29th day of August 1972.

(SEAL) I Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissionerof {Patents

2. A multi-trace pattern discriminating filter as set forth in claim 1wherein said output means comprises: time domain filter means forselectively receiving summed output from one of said summation means togenerate a plurality of time displaced outputs each delayed by apreselected different time; and spiking weighting means receiving eachof said time displaced outputs to effect preselected polarization andattenuation in accordance with time delay position, and to sum alldisplaced and attenuated outputs to provide a time analog output signalindicative of a selected component of reflection seismic energy.
 3. Amulti-trace pattern discriminating filter as set forth in claim 1 whichis further characterized in that: each timE domain filter of said firstpattern filter delays each respective one of the plurality of timedelayed outputs by the same increment; each time domain filter of saidsecond pattern filter delays each respective one of the plurality oftime delayed outputs by the same increment; and each time domain filterof said third pattern filter delays each respective one of the pluralityof time delayed outputs by the same increment.
 4. A multi-trace patterndiscriminating filter as set forth in claim 1 wherein each of saidweighting networks comprises: a plurality of attenuators each receivinga selected time delayed output to generate an attenuated output, eachattenuator adjusting a respective time delayed output to a selectedmagnitude which is said function of a characteristic operator for aselected component of the particular one of said plural traces whichwere applied to the respective time domain filter providing said timedelayed outputs; and attenuator summing means receiving attenuatedoutputs from each of said plurality of attenuators to provide saidsummed output.
 5. A multi-trace pattern descriminating filter as setforth in claim 4 wherein said output means comprises: time domain filtermeans for selectively receiving summed output from one of said summationmeans to generate a plurality of time displaced outputs each delayed bya preselected different time; and spiking weighting means receiving eachof said time displayed outputs to effect preselected polarization andattenuation in accordance with time delay position, and to sum alldisplaced and attenuated outputs to provide a time analog output signalindicative of a selected component of reflection seismic energy.
 6. Amulti-trace pattern discriminating filter as set forth in claim 1wherein said output means comprises: selective input means for receivinga selected one of said time analog signal outputs; operational amplifiermeans receiving said time analog signal output for amplification toprovide an output voltage, said amplifier means including a feedbackinput; a delay line having plural, time displaced outputs and a signaloutput and receiving said output voltage at an input; variableattenuating means each connected between a different one of said timedisplaced delay line outputs and said feedback input, said attenuatingmeans for each time displaced output being set in accordance with apreset time analog operator; an output device receiving said delay linesignal output for representation as a selected energy component withinsaid multiple traces of seismic data.
 7. Apparatus for processingmulti-trace seismic information by effecting exclusive extraction ofplural data indications each having predetermined energycharacteristics, comprising: means for dividing said multi-trace seismicinformation into plural, parallel groups of plural trace inputs; firstconvolution means receiving a first group of said plural trace inputsfor separately convolving each input with a trace operatorrepresentative of time and amplitude characteristics for energytraveling a first selected path to generate a respective convolutionoutput for each of said trace inputs; second convolution means receivinga second parallel group of said plural trace inputs for separatelyconvolving each input with a second predetermined trace operatorrepresentative of time and amplitude characteristics for energytraveling at a second selected path which is different from said firstselected path to generate a respective convolution output for each ofsaid trace inputs; third convolution means receiving a third parallelgroup of said plural trace inputs for separately convolving each inputwith a third predetermined trace operator representative of time andamplitude characteristics for energy traveling a third selected pathwhich is different from said first and second selected paths to generatea respective convolution output for each of said Trace inputs; and aplurality of summation means for separately summing the pluralconvolution outputs from each of said first, second and thirdconvolution means to generate first and second generalized indicationsof trace energies along said first, second and third reflection paths.8. A method for processing multi-trace seismic information by effectingexclusive extraction of plural data indications each havingpredetermined energy characteristics, comprising the steps of: dividingsaid multi-trace seismic information into plural parallel groups ofmulti-trace inputs; convolving each trace of each group with apredetermined operator which is representative of time and amplitude ofenergy traveling a selected path as determined by the pseudoinversematrix function for the selected path, the respective operators of afirst group representing primary reflection for each trace, therespective operators for a second group representing multiple reflectionfor each trace; separately summing convolved traces of each group toprovide a group convolution trace representing reflectioncharacteristics for selected seismic energy forms traveling selectedpaths.
 9. A method for processing multi-trace seismic information byeffecting exclusive extraction of plural data indications each havingpredetermined energy characteristics, comprising the steps of: dividingsaid multi-trace seismic information into plural, parallel channels;convolving each input of multi-trace information from first and secondchannels with respect to first and second predetermined time analogoperators representative of primary and multiple components ofreflection energy as determined by the pseudoinverse matrix function forthe respective energy components to produce first and second outputrepresentations neither of which contains any indication of energycommon to the other; recompressing said first and second outputrepresentations to obtain an indication of the primary and multiplecomponents of energy, respectively.
 10. A method as set forth in claim 9which is further characterized to include the steps of: convolving eachinput of multi-trace information from a third channel with a respectivethird predetermined time analog operator representative of aninterference component of reflection energy to produce a third outputrepresentation containing no indication of energy common to that of saidfirst and second output representations; recompressing said third outputrepresentation to obtain an indication of the interference component ofenergy within said multi-trace information.